Radiotelegraphy signaling system



May 8, 1923.

C. C. CHAPMAN RADIO TELEGRAPHY SIGNALING SYSTEM Filed April 27, 1920 Patented May 8, 1923.

CORWIN C. CHAPMAN, OF rALO ALTO, CALIFORNIA, ASSIGLNOR TO AUGUSTUS TAYLOR,

OF SAN FRANCISCO, CALIFORNIA. v I

RADIOTELEGBAPHY SIGNALENG SYSTEM.

Application filed April 27, 1920. Serial No. 376,942.

To all whom it may concern:

Be it known that I, Conwm C. CHAPMAN,

a citizen of the United States, and a resident of Palo Alto, county of Santa Clara, and State of California, have invented certain new and useful Improvements in Radiotelegraphy Signaling Systems, of which the following is a specification.

This invention relates to radio signaling and particularly to single wave radio signaling.

Heretofore, signaling with continuous oscillations produced by an arc radio generator has involved the radiation of oscillations of two frequencies, one being the signaling frequency or wave, and the other being the compensating frequency or wave. Signaling has usually been accomplished by variation of antenna inductance, which variation altered the frequency of the radiated wave, so that two waves of different frequency were radiated by a station during signaling. In order to avoid interference, it was necessary to assign two wave lengths to each station and as the number of stations have multiplied, confusion and interference has been caused by the radiation of oscillations of two different wave lengths from each station.

An object of the invention is to provide a system of single wave radio signaling, in which waves having a frequency above the limit of audibility are. converted into signals having a frequency within the range of andibility. The are radio generator produces continuous waves having a frequency above -the range of audibility, but many receiving stations are not equipped to receive and identify waves of such frequency. This invention, therefore contemplates so manipu- :lating the high frequency waves that signals will be received by such stations and this is preferably accomplished by converting the continuous wave into wave trains or wave groups, the frequency of the groups being within the range of audibility, so that signals so transmitted are readily received by all receiving stations. This is accomplished with the use of waves of a single frequency, thus eliminating the presence of the compensating wave. With my invention, there is utilized an absorbing oscillatory circuit in shunt with the transmitting circuit so that intermittently this shunt circuit absorbs substantially'fall of the energy of the source.

Another object of the invention is .toprovide a system of signaling as above described which requires the handling of only relatively small currents.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description, where those several embodiments of the invention which have been selected for illustration in theaccompanying drawings, will be outlined in full. It is to be understood, however, that the invention as expressed in the claims is not limited to the specific embodiments shown in the drawings. I I

Referring to said drawings:

Figure 1 is a diagrammatic representation of one form of system involving variation of the electrical constants of an oscillatory shunt circuit. 4

Figure 2 is a diagrammatic representation of modified form of the system shown in Figure l. i Y

Figure 3 is a diagrammatic representation of one form of system involving variation of the electrical constants ofthe antenna circuit andthe oscillatory shunt circuit.

In accordance withthis invention, ,the electrical constants of one or two oscillatory circuits are varied to cause the arc to oscillate intermittently on the antenna only when the signalingkey is depressed, so that groups of high frequency waves are radiated, the group frequency being within ,the

range of audibility.

Thesystem shown in Figure 1 comprises a source of'continuous oscillations,such as the are 2, which operatesin a hydrogen atmosphere. The are generator is grounded on one side, preferably the negative, and connected on the other side to the antenna 3 through the variable inductance 4. Direct current is supplied to thearc generator by the generator 5 and combinedmagnetizing and choke coils,,78 are arranged inthe positive lead, the coils surroundingmagnetic cores arranged adjacent the arc, so that the arc is subjected to a strongtransverse magnetio field. Shunting the arc is an oscillatory shunt circuit containing an inductance 12 and a capacity 13, and thiscircuit has slightly different electrical time con stants than the antenna circuit. .When an a shunted by tw .os io y ci ui ha g di ferent elect al im westerns-i the oscillatory shunt circuit.

may be made to oscillate principally on one circuit, to the practical neglect of the other. The electrical constants of the shunt oscillatory circuit are such that the arc ordinarily prefers to oscillate on the shunt circuit to the practical neglect of the antenna circuit. This shunt circuit thus absorbs substantially all of the energy supplied while no energy is radiated from the antenna.

shunting a portion of the inductance 12 is a circuit containing a resistance l l, an interrupter l5 and a key 16. Assuming that the interrupter is eliminated, closing the key 16 will close the resistance circuit, increase the resistance of the oscillatory shunt circuitand cause the arc to oscillate practically entirely on the antenna circuit. lVhen the key is closed, a radio frequencycurrent will flow through the resistance, causing an energy loss so that the resistance has the equivalent effect of being inserted directly into lhe current through the resistance is probably not only the antenna current, but also a certain amount of induced current due to the transformer action of the inductance 12, which becomes in effect an auto-transformer. It is preferable to make the value of the resistance in ohms substantially equal to the reactance in ohms at radio frequency of the turns of the inductance shunted by the resistance circuit, in order to cause a maximum energy loss in the resistance.

\Vhen the key is open, the arc oscillates practically entirely on the oscillatory shunt circuit and when the key is closed, the arc oscillates practically entirely on the antenna circuit consequently waves are radiated only when the key is closed. The interrupter 15, in the resistance circuit, is rotated by any suitable means at such speed that the resistance circuit, when closed by the key, is interrupted at a' frequency within the range of audibility. This produces the radiation from the antenna, when the key is closed, of groups of waves, the group frequency being within the range of" audibility, so that the groups may be received and detected by receiving devices which would not be responsive to the high frequency continuous waves. The speed of the interrupter is, of course, sufliciently high that the resistance circuit is interrupted many times while the key is depressed during signaling.

In Figure 2 there is shown a modified form of single wave group frequency system in which the commutator or interrupter 1'7 acts to alternately direct the current to the shunt oscillatory circuit and the antenna circuit, when the key 18 is closed, on the antenna circuit. One. side of the shunt cir- Quit is connected to the commutator by two conductors 21 and 22, so that when the key isclosed on the shunt circuit the arc oscil lates continually on that circuit and when the key is closed on the antenna circuit the arc oscillates alternately on the antenna and shunt circuits, thereby producing the radiation of groups of Waves, the group quency being within the range of audibility. In the system shown in Figure 3, the time:

constants of the antenna and of the shunt oscillatory circuit are oppositely varied by the closing of the key, so that conditions in one circuit are made more favorable for oscillation and conditions in the other circuit are made less favorable. In this system, the antenna circuit and the shunt oscillatory circuit may or may not be tuned to the same frequency. Inductively connected to the antenna inductance 4 is a circuit 9A and inductively connected to the shunt circuit inductance 12 is a circuit 25, the two circuits being provided with a commonshunt including the interrupter 26, the key 27 and the resistance 28. \Vhen the key is open, the

arc oscillates on the shunt oscillatory cir- 1. A radio telegraphy signaling system,

comprising a source of continuous radio oscillations, a radiating circuit connected to said source, an oscillatory absorbing circuit also connected to said source, an energy abn sorbing element, and means for coupling said element alternately to one or the othe circuit at audio frequency.

2. A radio telegra-phy signaling system, comprising a source of continuous rad-i0 oscillations, a radiating circuit connected-to said source, an oscillatory absorbing circuit connected to said source, an energy absorbing element, a circuit coupled to the radiating circuit, a circuit coupled to the absorbing circuit, said coupled circuits being so arranged that the energy absorbing element forms a common path for both coupled circuits, and means for alternately completing the coupled circuits at audio frequency.

3. A radio telegraphy signaling system,

comprising a source of continuous radio oscillations, a radiating circuit connected to said source, an oscillatory absorbing circuit connected to said source, a pair of circuits, one inductively coupled to the radiating circuit and the other to the absorbing circuit, and means for alternately completing said circuits at audio frequency.

4. A radio telegraphy signaling system, comprising a source of continuous radio oscillations, an antenna circuit connected to said source, an oscillatory absorbing circuit shunting said source, a circuit inductively coupled to the antenna circuit, a circuit in ductively coupled to the absorbing circuit, and means rendering these circuits efi'ective and ineffective at audio frequency, whereby groups of radio Waves are transmitted and the shunt circuit absorbs the energy during periods of rest of the antenna circuit.

In testimony whereof, I have hereunto set my hand.

OORWIN o. oHArMAN. 

